The toolbox is, as said, a mounting place for many more (vibrating) parts and is therefore made sturdy. The airfilter bracket is also attached to it. To repair the locks I used TZ250 cowling Dzus fasteners, which are still available.

Yamaha YDS2, toolbox

From these details you can see the sturdy construction of the bike. Here Yamaha still used 8 mm bolts with 14 mm heads, that changed quickly to slimmer dimensions!